The invention relates to an optical multiplexer device which includes a plurality of optical fibers. One end face of each optical fiber is arranged in a common plane. The fibers include a first optical fiber for conducting several light signals of different wavelengths, and at least two second optical fibers each of which conduct a light signal in a single waveband.
The device further includes a wavelength-selective element, and a lens system which is arranged between the wavelength-selective element and the common plane. The arrangement is such that a low-attenuation transmission path which is dependent on the wavelength of the light is formed between the first optical fiber and each of the second optical fibers.
The optical multiplexer device may be a multiplexer as well as a demultiplexer. In the former case, the second optical fibers provide the input signals while the first optical fiber receives the output signal. In the latter case, the first optical fiber is the input fiber while the second optical fibers are output fibers. A device of this kind is described in European Patent Application No. 74,152.
The construction of the device described above is comparatively complex. This is due, inter alia, to the fact that the orientation of the wavelength-selective element with respect to the incident light beam is adjustable. In many cases, however, it is sufficient to adjust the device properly during assembly; adjustability during operation is then no longer necessary. In such cases it is notably important that the cost of the device be as low as possible.